<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>属性</title>
</head>
<body>
<div class="cls">第1个</div>
<div class="cls">第2个</div>
<div id="1">第3个</div>
<div id="2">第4个</div>
<div style="background-color: aqua">第5个</div>

</body>
</html>